Not applicable.
Not applicable
The present invention relates to a system and method for automatic shutdown and restart of a locomotive engine with a low engine lube oil protection mechanism.
Applicant""s SmartStart(copyright) system is a locomotive automatic shutdown and restart system. It offers railroads significant fuel savings by reducing unnecessary idling time. It is a mature device that has been available for over 10 years. Applicant""s SmartStart(copyright) system was patented in U.S. Pat. No. 5,265,567, the entire contents of which are hereby incorporated by reference.
The SmartStart(copyright) system, as well as any other locomotive automatic shutdown and restart system, must be applied such that it does not interfere with the locomotive""s original protection devices. Yet, on many locomotives, these devices may prevent a successful automated restart.
One such engine protection mechanism is the engine low oil button. This mechanism is built into the locomotive""s engine speed governor and is found on the majority of North American and export locomotives. This device senses the engine oil pressure, and if it is below a safe limit, will shut the engine down.
FIG. 1 is a typical prior art engine lube oil configuration on an EMD locomotive with a mechanical governor. Oil is sourced from the engine""s sump, conditioned to be cleaned and cooled, then forced through the engines pistons, bearings and other moving components.
There are typically 12 to 16 power packs (cylinder assemblies) in an engine. Thus, there is a delay on start-up to achieve the required pressure on the last cylinder and bearing assembly. At this point, a line is piped to the engine""s governor.
Within the governor, an isolated system is used to generate internal governor pressure. The governor""s internal oil pressure is placed on one side of a diaphragm and matched against engine oil pressure on the other side. If this is balanced, the governor functions normally. A design feature of the governor is to allow the engine oil pressure approximately 60 seconds to build up before enabling the low oil pressure shutdown feature. If the engine oil pressure is low after this dwell period, which is applicable only after engine start-up, the governor will shut off the fuel supply to the engine. This will result in the engine shutting down. Once the governor""s low oil mechanism trips, it needs to be physically reset. This is done by either manual intervention, or by an exterior device that is controlled by the automated shutdown restart system. While effective, the latter is expensive, awkward to install, and impedes regular maintenance of the governor.
There are several reasons that might create a low oil condition causing a trip in the governor""s protection mechanism. The most obvious is a genuine low oil pressure condition, caused by a blockage in the lube oil""s path, a problem with the pump, a leak in the engine""s sump or any number of other legitimate reasons.
Unfortunately, a small group of locomotives are susceptible to unwarranted trips of the low oil button by taking more than the allotted time to initially build up pressure when starting up. Another small group will experience unwarranted trips as a result of shutting down on the engine. This is caused by a race condition where the engine oil pressure drops extremely rapidly in relationship to the governor""s internal oil pressure. Other causes of nuisance low oil button trips include shockwaves in the lube oil supply lines created by jerky motions in the engine""s crankshaft during the startup or shutdown process. Regardless of the cause, the result is predictable and will prevent the locomotive from being automatically restarted until the governor low oil button is physically reset.
As mentioned earlier, the SmartStart(copyright) system does offer a cumbersome and expensive product that will effectively reset the low oil button during shutdown and start up. Some railroads have utilized this device successfully.
Other railroads have attempted to resolve this issue by replacing the governor and other engine components. This can be very expensive and time consuming. In some cases, extensive attempts have not resolved the issue.
What is needed is a relatively inexpensive solution that is easy to apply, does not interfere with the governor""s normal maintenance, and reliably prevents the locomotive from shutting down unnecessarily during automatic startup or shutdown.
Applicants have solved the problems discussed above by adding a solenoid valve between the engine and the governor oil pressure sensor. Upon automatic engine shutdown, the solenoid valve is closed, thereby maintaining the existing engine oil pressure on the governor oil pressure sensor. The valve is kept closed until a short period, such as 1 minute, after the engine is automatically restarted.